The role of circadian rhythms in Obstructive Sleep Apnea symptoms and novel targets for treatment

Obstructive sleep apnea may induce sleep-wake cycle dysregulation: An actigraphic study

Obstructive sleep apnea (OSA) causes sleep fragmentation and excessive daytime sleepiness (EDS). OSA has been hypothesised to impair the circadian sleep-wake rhythm, and this dysregulation may in turn exacerbate OSA-related diurnal symptoms. Hence, this study aimed to assess the sleep-wake rhythm through actigraphy, and its relationship with EDS in patients with untreated OSA. Patients with moderate-severe OSA (apnea-hypopnea index ≥15/h) and healthy controls (HC) underwent a 7-day actigraphic recording to evaluate the sleep-wake rhythm. Participants underwent a sleep medicine visit and completed the self-report questionnaires assessing EDS (Epworth sleepiness scale, ESS), sleep quality (Pittsburgh sleep quality index, PSQI), and chronotype (morningness-eveningness questionnaire, MEQ). This study included 48 OSA patients (72.9% males; mean age 56.48 ± 9.53 years), and 22 HC (45.5% males; mean age 53.73 ± 18.20 years). After controlling for MEQ scores, actigraphic recording showed that the OSA patients present a lower sleep time (p = 0.011) and sleep efficiency (p = 0.013), as well as a higher sleep latency (p = 0.047), and sleep fragmentation (p = 0.029) than the HC. Regarding the sleep-wake rhythm actigraphic parameters, the OSA patients showed a lower average activity during the most active 10-hour period (p = 0.036) and a lower day/night activity ratio (p = 0.007) than the HC. Patients with OSA also reported higher ESS (p = 0.005) and PSQI scores (p < 0.001), and a chronotype less of morning type (p = 0.027) than the HC. In conclusion, this study documented a reduced diurnal motor activity and lower day/night activity ratio in OSA patients than in controls. These findings suggest a dysregulation of the circadian sleep-wake rhythm in OSA, possibly related to both EDS and reduced daytime motor activity.

Bright light therapy for CPAP-resistant OSA symptoms

STUDY OBJECTIVES

Sleep fragmentation and daytime sleepiness often persist in patients with sleep apnea despite correctly administered continuous positive airway pressure (CPAP). Our proof-of-concept study tested the acceptability and efficacy of morning bright light therapy (BLT) to improve sleep, circadian rhythms, and CPAP-resistant daytime symptoms in patients with sleep apnea.

METHODS

In this within-subject crossover study, 14 individuals completed 4 weeks of BLT and sham BLT in randomized order. Outcomes included actigraphy-based objective sleep measures, sleepiness, depressive symptoms, and sleep-related functional impairment, analyzed with multilevel models.

RESULTS

Patients experienced greater reductions in wake after sleep onset and increased amplitude of rest-activity rhythms in a shorter photoperiod with BLT compared with sham. Patients also reported reductions in self-reported sleepiness and depressive symptoms with BLT compared with sham only during the early stages of treatment and shorter photoperiod.

CONCLUSIONS

These results suggest the potential for novel applications for existing chronotherapeutic interventions for improving symptoms and quality of life for those patients who experience residual symptoms with current available treatments.

CLINICAL TRIAL REGISTRATION

Registry: ClinicalTrials.gov; Name: Bright Light Therapy for Residual Daytime Symptoms Associated With Obstructive Sleep Apnea; URL: https://clinicaltrials.gov/ct2/show/NCT04299009; Identifier: NCT04299009.

CITATION

Soreca I, Arnold N, Dombrovski AY. Bright light therapy for CPAP-resistant OSA symptoms. J Clin Sleep Med. 2024;20(2):211-219.

New insights from integrated bioinformatics analysis: the role of circadian rhythm disruption and immune infiltration in obstructive sleep apnea disease

Background

Circadian rhythm disruption and immune infiltration are both closely associated with the development of Obstructive sleep apnea (OSA) disease and a variety of cardiovascular and neurological complications, but their interactions with OSA disease are not clear. In this study, we used bioinformatics to investigate the roles of circadian rhythm disruption and immune microenvironments in OSA.

Methods

We analyzed differential genes and their associated functional pathways in the circadian rhythm-associated OSA dataset, then regrouped OSA samples using the differential genes and explored differences in immune cell infiltration between the two different subgroups. Meanwhile, we used two machine learning algorithms to further define circadian rhythm-related signature genes and to explore the relationship between key genes and immune cell infiltration. Finally, we searched for the transcription factors of the key differential gene JUN.

Results

We screened 15 circadian rhythm-related differential genes in the OSA-related dataset and further defined 3 signature genes by machine learning algorithms. Immunoassays showed a significant increase in resting mast cell infiltration and a decrease in monocyte infiltration in the OSA group. The results of our animal experiments also confirmed that the expression of these 3 key genes, as well as the immune cell infiltration, showed a trend consistent with the results of the bioinformatics analysis.

Conclusions

In conclusion, this study reveals the interaction between circadian rhythm disruption and immune infiltration in OSA, providing new insights into the potential pathogenesis of OSA.

Is obstructive sleep apnea a circadian rhythm disorder?

Obstructive sleep apnea is the most common sleep-related breathing disorder worldwide and remains underdiagnosed. Its multiple associated comorbidities contribute to a decreased quality of life and work performance as well as an increased risk of death. Standard treatment seems to have limited effects on cardiovascular and metabolic aspects of the disease, emphasising the need for early diagnosis and additional therapeutic approaches. Recent evidence suggests that the dysregulation of circadian rhythms, processes with endogenous rhythmicity that are adjusted to the environment through various cues, is involved in the pathogenesis of comorbidities. In patients with obstructive sleep apnea, altered circadian gene expression patterns have been demonstrated. Obstructive respiratory events may promote circadian dysregulation through the effects of sleep disturbance and intermittent hypoxia, with subsequent inflammation and disruption of neural and hormonal homeostasis. In this review, current knowledge on obstructive sleep apnea, circadian rhythm regulation, and circadian rhythm sleep disorders is summarised. Studies that connect obstructive sleep apnea to circadian rhythm abnormalities are critically evaluated. Furthermore, pathogenetic mechanisms that may underlie this association, most notably hypoxia signalling, are presented. A bidirectional relationship between obstructive sleep apnea and circadian rhythm dysregulation is proposed. Approaching obstructive sleep apnea as a circadian rhythm disorder may prove beneficial for the development of new, personalised diagnostic, therapeutic and prognostic tools. However, further studies are needed before the clinical approach to obstructive sleep apnea includes targeting the circadian system.

Obstructive Sleep Apnea, Circadian Clock Disruption, and Metabolic Consequences

Obstructive sleep apnea (OSA) is a chronic disorder characterized by recurrent episodes of apnea and hypopnea during sleep. It is associated with various cardiovascular and metabolic complications, including type 2 diabetes mellitus (T2DM) and obesity. Many pathways can be responsible for T2DM development in OSA patients, e.g., those related to HIF-1 and SIRT1 expression. Moreover, epigenetic mechanisms, such as miRNA181a or miRNA199, are postulated to play a pivotal role in this link. It has been proven that OSA increases the occurrence of circadian clock disruption, which is also a risk factor for metabolic disease development. Circadian clock disruption impairs the metabolism of glucose, lipids, and the secretion of bile acids. Therefore, OSA-induced circadian clock disruption may be a potential, complex, underlying pathway involved in developing and exacerbating metabolic diseases among OSA patients. The current paper summarizes the available information pertaining to the relationship between OSA and circadian clock disruption in the context of potential mechanisms leading to metabolic disorders.